Fight Against Fever Ticks is Slow

A few miles north of the Rio Grande, where spring temperatures climb past 100 degrees, helicopters work in concert with cowboys to gather cattle, thorny bushes nick kneecaps, and dust and manure swirl up noses and down collars, and cowboys inspecting, dipping or treating cattle are gritty and soaked with sweat before noon.

For a small contingency of government “hands” and livestock producers on the border, the very presence or absence of ticks on cow bellies or deer flanks indicate defeat or victory in the fight against the fever tick, a foreign-origin pest that threatens the health of U.S. cattle.

This is the scene that Mr. Bruce Knight, USDA’s undersecretary of agriculture for marketing and regulatory programs, traveled to South Texas to see in mid-March to gain a first-hand perspective of the fever tick situation. He visited a fever tick-infested premises, observed gathering and treatment of cattle, and discussed fever tick issues with ranchers, USDA and TAHC staff.

Mr. Knight noted the time, work and expense endured by cattlemen to round up cattle and present them for treatment. He also experienced the difficulty in gathering cattle in the brush country of South Texas, where a helicopter is as necessary as cowboys on horseback.

“We are fighting a border war against the fever tick,” said Dr. Bob Hillman, Texas’ state veterinarian and head of the Texas Animal Health Commission, the state’s livestock and poultry health regulatory agency.

“I believe Mr. Knight’s visit to the fever tick quarantine area will result in a commitment and dedication of resources necessary to successfully operate the fever tick program.”

In 1943, the U.S. pushed the fever tick across the border and has maintained a permanent quarantine zone along the Rio Grande from Del Rio to Brownsville, Texas, since that time as a deterrent to re-infestation with the fever tick. However, the tick was never eradicated from Mexico, which serves as a continuous source for reintroduction into US cattle herds.

“Last summer the pest gained a foothold beyond the 852-square mile permanent, USDA-patrolled fever tick quarantine zone,” said Dr. Hillman.

“As of mid-March 2008, we are making progress in fighting the outbreak, having defined the outer limits of the tick’s spread. Now the TAHC, USDA and livestock producers are working from the “outside in” to eradicate the tick, a process that may take another 16 to 18 months, if no additional infestations are discovered.”

“Due to fever tick infestations, more than 1,000 square miles of ranchland have been temporarily quarantined since last summer. The quarantines are in Starr, and Zapata counties, and in a contiguous area of Maverick, Dimmit and Webb counties,” Dr. Hillman said. “From these areas, no domestic or exotic livestock capable of hosting the fever tick can be moved without an inspection, treatment and a permit. These temporary quarantines more than doubled the geographic scope­to an area larger than Rhode Island and Washington, D.C.–for which fever tick monitoring, inspection and treatment must be provided.”

“The battle costs money, but fighting the battle against fever ticks has been like putting a band aid on a lacerated artery,” said Dr. Hillman. Beginning in August 2007, the TAHC worked with the U.S. Department of Agriculture to develop a funding request, which if fulfilled, would be sufficient to provide the personnel, equipment and supplies required to contain, and then eradicate the fever tick outbreak from the temporarily quarantined areas.

On March 19, 2008, USDA announced that $5.2 million, would be made available to control the outbreaks of fever ticks occurring outside the permanent quarantine zone between Texas and Mexico. “We are very appreciative that these funds are being provided to aid in the fight against the fever tick,” said Dr. Hillman. “They will certainly help in this battle against a relentless foe. However, this level of funding is significantly less than the $13 million requested and will be enough to address only the program’s most dire needs.”

“If we are to be ultimately successful in eliminating fever ticks from the temporarily quarantined areas, and push the fever ticks past the permanent quarantine zone and back into Mexico, we must have sustained funding over many years. The amount provided will be utilized efficiently, but it will not be sufficient to complete the job,” said Dr. Hillman.

Besides the sheer size of the area under quarantine, nearly 100 premises (up from 40 premises in 2007) in the permanent and temporarily quarantined areas are known to have fever ticks. On these pastures, livestock must be examined and treated every 14 to 28 days, depending on the acaracide products used. As an alternative, the animals can be “tick-free” for two consecutive treatments, then transferred under permit from the property, leaving the pasture vacant for at least nine months, with the idea that the ticks will starve. Because the fever tick has shown an ability to adapt to wildlife hosts, pasture vacation may no longer be an effective option for
‘clearing’ a pasture of fever ticks.

Since October 1, 2007 (the start of federal fiscal year 2008) more than 52 fever tick infested premises have been detected in the permanent and temporary quarantine areas. During the 2007 hunting season, about 2,300 white-tailed deer and other wildlife hosts harvested in the quarantined areas were examined for fever ticks by the USDA and TAHC.

Inspections disclosed that, of the 52 newly detected fever tick-infested premises, 23 premises had fever tick-infested wildlife. Fever ticks were detected on white-tail deer, fallow deer, axis deer, and red deer. The pests also were found on aoudad sheep, a species previously not thought to be a fever tick host.

“This is disturbing, but not surprising,” said Dr. Hillman. “Wildlife host populations are high in these areas. Scientists believe that the fever tick prefers cattle as a host, but when tick populations are unchecked, or cattle hosts are not available, the pest will infest wildlife hosts.”

Fever tick-infested wildlife complicates eradication. Treatment for free-ranging wildlife is limited to feeding ivormectin-treated corn or drawing animals to ‘four-poster’ stations where they rub against pyrethrin-treated posts, which transfers the chemical to the head, neck and ears of animals and kills the ticks. However, some products require a 60-day withdrawal period, so they can’t be used just prior to or during the hunting season.

One of the most time-consuming and frustrating tasks in the fever tick fight has been tracing the more than 800 head of cattle moved from the area since August 2006. TAHC staff spent several months looking for the animals, due to a scarcity of records and animal identification. Most of the shipments had moved within Texas, but some animals had been transported as
far away as Kansas, Colorado, Oklahoma and Wyoming. All the animals have been inspected, and none were infested with the fever ticks.

“The very success of the fever tick program may be its biggest problem. The USDA’s Fever Tick Force has run for years under-funded, understaffed, but without a whimper. This small crew has held back the tick onslaught for years,” said Dr. Hillman.

It is time to remember why this tiny, prolific pest is so deadly to cattle, he noted. Fever ticks by themselves are a problem. Fever ticks that carry the blood parasite, “babesia,” are deadly and can infect cattle with “cattle tick fever,” causing them to suffer bloody urine, diarrhea, fever and extreme anemia before death.

“We either address the fever tick in south Texas, or we could be addressing fever ticks in Oklahoma, Missouri, Virginia, California, or a host of other states where the tick would flourish,” said Dr. Hillman. “Fever ticks are not just a “Texas” problem. Through extraordinary effort by cattlemen, and state and federal animal health officials – beginning in 1906 and culminating in 1943–these pests and babesiosis, the disease they carried, were eradicated from the United States. These fever ticks are now classified as foreign pests, and they are a U.S. problem.”